1. Field of the Invention
The present invention relates to a method of driving a matrix driving display device which displays one color by combining a plurality of basic colors, for example, red (R), green (R), and blue (B).
2. Description of the Related Art
Hitherto, a liquid-crystal display device has been known in which a display element, such as a liquid crystal, is used, and this is combined with a light source and color filters, making color display possible.
Here, a description will be given below using a liquid-crystal display device of the following thin-film transistor driving method as an example: in color filters, a pixel which displays one color is formed by combining and using the three basic colors of R, G, and B each as a dot, a large number of these pixels are arrayed in a display area, and further, signal lines and scanning lines are wired in a matrix form in order to drive the liquid crystal, pixel electrodes are arranged in an area which is partitioned by the signal lines and scanning lines, switching of the pixel electrodes is performed by thin-film transistors and an electric field is applied to a liquid crystal corresponding to each dot, causing the transmittance of the liquid crystal to vary so as to switch between display and non-display.
In a display device for a computer to which this type of liquid-crystal display device is applied, in a VGA (Video Graphics Array) display device which makes a display of 640 (horizontal).times.480 (vertical) dots, the number of pixels (one pixel being formed by a set of each one of the dots R, G. and B), which is the display unit, is 640.times.480=307,200, and since these are divided into three parts along the signal lines, the number of scanning lines are 480, and the number of signal lines are 640.times.3=1,920. Therefore, the total number of dots is 640.times.3.times.480=921,600.
FIG. 20 shows a color liquid-crystal drive unit having a driving LSI mounted to the screen of this type of color liquid-crystal display device. In FIG. 20, reference numeral 1 denotes a liquid-crystal display device in which a liquid crystal is sealed between two transparent substrates disposed in such a manner as to face each other, a common electrode and color filters are provided on one transparent substrate, a large number of signal lines along the vertical direction and a large number of scanning lines along the horizontal direction are wired in a matrix form on the other transparent substrate, and pixel electrodes and thin-film transistors are provided in an area which is surrounded and partitioned by the signal lines and the scanning lines. In this example, a plurality of gate drivers Gd for driving scanning lines are mounted on the side of the left-side section of the liquid-crystal display device 1, and a plurality of source drivers Sd for driving signal lines are mounted on each of the upper-edge side and the low-edge side.
FIG. 21 shows the circuit configuration of the liquid-crystal display device 1 of this example. In the circuit of this example, a large number of signal lines S.sub.1, S.sub.2, S.sub.3 in vertical sequences, and scanning lines G.sub.1, G.sub.2 in horizontal sequences are formed on the circuit of this example in such a manner as to intersect each other, with pixel electrodes 5 and thin-film transistors 6 being provided in areas partitioned by the signal lines and scanning lines, one area having the pixel electrode 5 formed therein is made to represent one dot, and a set of three dots is made to represent one pixel.
Therefore, in the circuit shown in FIG. 20, since a pixel 7 such as that surrounded by the chain line in FIG. 21 is formed, in the VGA display device described above, 307,200 of these pixels 7 are formed on one screen.
The source drivers Sd and the gate drivers Gd provided in the liquid-crystal display device 1 having such a number of dots are ordinarily formed from one LSI having about 240 output pins. Therefore, the mounting of the LSI on a transparent substrate of the liquid-crystal display device 1 is conventionally in the form of TCP (Tape Carrier Package) which uses an LSI mounted onto polyimide tape, or in the form of COG (Chip on Glass) which directly mounts an LSI.
Therefore, in order to handle 1,920 signal lines and 480 scanning lines used in the liquid-crystal display device 1, as shown in FIG. 20, it is necessary to use 8 (240.times.8=1,920) source drivers Sd with 240 pins and 2 (240.times.2=480) gate drivers Gd with 240 pins. Although in an actual liquid-crystal display device, in addition to these, a circuit for providing a signal or the like to a driver is required separately, a description thereof has been omitted here.
Here, regarding power consumption of the drivers, it is assumed that the power consumption of the source driver Sd is larger than that of the gate driver Gd, as will be described below.
Driver power consumption (approximately 840 mW)
Gate driver Low (approximately 20 mW.times.2=40 mW: occupies 5%) PA2 Source driver High (approximately 100 mW.times.8=800 mW: occupies 95%)
It is also known that the unit price of the source driver is generally more expensive by approximately twice than that of the gate driver.
At present, the power consumption of the source driver is a typical power consumption of 6 bits (number of gradations: 64) in color display. In the case of 8 bits, both the price and the power consumption are increased in values, and the differences in price and power consumption between the gate driver and the source driver become larger. Against the above background, in order to achieve a lower cost and a lower consumption of power of a liquid-crystal display device in which progress is being made towards a larger screen and a larger number of gradations, it is desirable to reduce the number of these expensive drivers required.
Further, if, in the exchange for the achievement of a low power consumption, the image quality deteriorates because of flicker or the like, this deterioration becomes markedly conspicuous because the screen is large. Therefore, it is necessary to achieve a lower power consumption and to maintain the quality of images.
An object of the present invention, which has been achieved in view of the above-described circumstances, is to provide a driving method which reduces the power consumption of a driving circuit system and which does not cause a decrease in the image quality in a display device in which pixels are arrayed such that a plurality of basic colors are combined to display one color and are matrix-driven.
To achieve the above-described object, according to the present invention, there is provided a method of driving a display device, in which a large number of pixels which display colors by combining a plurality of basic colors are arrayed, the large number of pixels are matrix-driven by a large number of scanning lines and a large number of signal lines, and the combinations of the plurality of basic colors are arrayed repeatedly along the direction of each signal line, and the number of scanning lines is determined at a number such that the number of corresponding pixels arrayed along one signal line is multiplied by the number of basic colors, the driving method comprising the steps of: dividing one frame of pixel display information into fields of a number equal to or greater than the number of basic colors; and scanning a reduced number of the scanning lines and displaying the basic colors at the same rate within each field.
Further, one frame described above is divided into the same number of fields as the number of the basic colors, and one frame described above is divided into fields of a number which cannot be divided by the number of the basic colors.
According to the present invention, there are the advantages that since one frame is divided into a plurality of fields and scanning is performed for each field, it is possible to drive a display device in the same way as when driving a conventional construction and to reduce the consumption of power.
Further, since scanning is performed so that the mutually different basic colors are displayed for each scanning line in the fields and that the frame is formed of fields for the number of basic colors, the display color being different for each field, it is possible to prevent flicker and the like. Specifically, there is the advantage that a display can be made such that it can be viewed very easily.
The above and further objects, aspects and novel features of the invention will become more apparent from the following detailed description when read in connection with the accompanying drawings.